1. Field of the Invention
The present invention concerns an audio signal processing unit and an audio transmission system, in particular a microphone system.
2. Description of Related Art
Audio signal processing units are known hitherto in various configurations, which together with a pickup unit such as a microphone can form an audio signal transmission system, in particular a microphone system. They have a pickup unit like a microphone to pick up an audio signal and pass it in wired or wireless fashion to the audio signal processing unit. That audio signal processing unit can subject that received audio signal to further processing itself such as for example it can filter it, record it, output it or pass it to corresponding further units such as a recording device, a filter, a mixing console, a loudspeaker or the like. That audio signal processing unit can also combine the audio signal received from the pickup unit itself with at least one further audio signal and record the joint combined signal, filter it, subject it to further processing or output it.
What is common to all the above-described audio signal processing units is that operation in order to influence the audio signal received from the pickup unit and/or further audio signals has to be implemented directly at the audio signal processing unit itself. Alternatively it is also possible, by means of a mixing console or the like which obtains from the audio signal processing unit the audio signal received from the pickup unit or a further audio signal or also an audio signal combined from those audio signals, to influence that audio signal or signals. Those influences include muting the pickup unit for example by the audio signal received from the pickup unit not being recorded, filtered, subjected to further processing or outputted. Equally, conversely, a further audio signal may not be recorded, filtered, subjected to further processing or outputted, so that only the audio signal received from the pickup unit is recorded, filtered, subjected to further processing or outputted. It is also possible for example for those signals to be combined together by way of a mixing console. Thus for example the sound and/or the level of a further audio signal can be controlled depending on whether a user does or does not talk into the pickup unit.
Those functions of a selection between various audio signals which are fed to the audio signal processing unit and also combining those audio signals by mixing them or by bringing them together is generally implemented in the form of a manual control by means for example of the audio signal processing unit or a mixing console with operating elements such as for example switches, sliding or rotary controllers. In that respect the operating elements are to be operated by a user to implement those functions. A disadvantage in that respect is that a second person is necessary beside the speaker to operate the audio signal processing unit or the mixing console, or that the speaker must have direct access to the audio signal processing unit or the mixing console and is correspondingly restricted in his freedom of movement.
Automatic muting of an output signal or an automatic reduction in a first audio signal when reaching a predetermined threshold value for the level of a second audio signal is also known, in which level reduction is effected for example in aviation headsets for external sound sources, for example during radio communication. A disadvantage here is that this mode of operation is susceptible to error as that automatic system also reacts in part to interference noises or switches into the mute state with a serious delay. The user can also not specifically targetedly control automatic muting or the automatic lowering of level. In addition known (aviation headset) systems only influence the level of the first audio signal source but do not afford any function for complete muting thereof.
Also known is an automatic mute function by means of a pilot tone signal evaluator (command function). In that respect in telecommunications the term pilot tone signal denotes a signal (generally a single frequency) which is transmitted outside and independently of the actual useful signal by way of a communication channel. That signal serves for checking, control, reference or monitoring purposes. Wireless microphones communicate for example with a pilot tone signal (switchable pilot tone signal monitoring) inter alia items of information such as a battery status check or the MUTE, switch status of the transmitter, that is to say the pickup unit or the microphone, to the receiver. Those data communicated by means of the pilot tone signal are evaluated in the pilot tone signal decoder of the receiver and displayed at the display of the receiver.
In that respect that command function or the pilot tone signal evaluator can be used in professional equipment for muting the audio signal of the pickup unit. A disadvantage in that case is that such systems can only use the pilot tone signal tests for muting and do not offer any mixing function with other audio signal sources.
Evaluation of the pilot tone signal (mute state) can also be effected by way of remote control software. That however can only represent the pilot tone signal, in contrast actions have to be performed by the user. In addition that networking is at the present time possible only with the devices having such remote control software, which however are more expensive than devices without it.
As general technological background attention is directed to DE 10 2004 052 296 A1 and EP 1 406 224 A2.